Non-volatile memory devices may be used in any application for storage of binary digits (or bits) of information that should be maintained even when the memory devices are not powered. An example of such devices are flash memory devices, each one of which typically includes a memory array, and peripheral circuits for functions of management and access thereto (such as, for example, decoder, reference voltage or band-gap generator, charge pumps).
At an appropriate phase of a production process of the memory device, the latter is generally subject to a parametric test to characterize the memory device, i.e. determine a measure value (or measure) of functional parameters thereof. The parametric test may represent a particularly burdensome aspect of the production process of the non-volatile memory devices, since it involves inefficiencies due to a reduced convenience and ease of measure where a relatively large number of functional parameters are to be measured.
For example, in a widely used approach, the parametric test is carried out through a technique known as electrical wafer sort (EWS). The parametric test implemented by the EWS technique is carried out on the memory devices yet included within a corresponding wafer of semiconductor material, and before the individual portions of the wafer on which the memory devices are integrated are diced into individual chips and embedded within respective packages.
The parametric test implemented by the EWS technique is executed on each memory device by automatic test equipment (ATE). The latter is provided with a test driver circuit (test driver) and a probe card including a plurality of conductive probes for contacting (operation called probing) corresponding conductive terminals (e.g., pads or pins) of the memory devices subject to the parametric test.
Typically, a test procedure (or routine) is run within the test driver to perform the parametric test. More particularly, such routine may include a memory instruction for the memory device, in response to which the latter performs a corresponding memory operation, and a sequence of test instructions, in response to which the test apparatus performs corresponding test operations for detecting a result of the memory operation and correspondingly determining the measure value of the functional parameter.
However, according to specific management protocols implemented within the memory device, each memory operation typically provides a result different in number and type (e.g., a voltage, a current, a string of bits, a synchronization signal, and the like). Thus, to characterize the memory device, it may be desirable, downstream from the memory operation, to process the result by specific auxiliary operative blocks (external and/or internal to the test apparatus) according to the functional parameter to be measured. Therefore, the test apparatus may be controlled by a specific routine for each functional parameter to be measured (for example, by configuring it to enable it to detect a determined type of result and/or a full reception of the same, or by setting it to allow the measurement of the functional parameter by exploiting the operative functional blocks within the test apparatus and/or external thereto).
For example, the characterization of the memory device by measuring functional parameters, such as band-gap time (time to generate the band-gap voltage), clock frequency of the charge pumps, and reading access time, may involve the implementation of corresponding routines different one to another. More specifically, to measure the band-gap time, the corresponding routine may provide the memory instruction to the memory device for performing the corresponding memory operation (band-gap voltage generation), and the test instruction to the test apparatus for monitoring an output terminal of the memory device (polling) until the complete reception of the result of the memory operation (band-gap voltage) and for enabling the measure of the band-gap time according to an elapsed polling time.
Instead, to measure the clock frequency of the charge pumps, the corresponding routine provides the memory instruction to the memory device for activating the charge pumps, and the test instruction to the test apparatus for enabling the test apparatus to receive the clock signal and provide the frequency value by exploiting proper circuits already present therein. Finally, to measure the reading time access, the corresponding routine provides the memory instruction to the memory device for performing a reading operation of a predefined memory address (typically provided together to the memory instruction), and the test instruction to the test apparatus for performing the polling to detect the result of the memory operation (read data) and controlling a detection block external to the test apparatus for enabling the measure of the access time (time interval between the sending of the predefined memory address and the arrival of the read data).
Therefore, the parametric test performed in this way provides for a continuous interaction with the test apparatus to set the latter according to the functional parameter to be measured. This makes the parametric test long and not efficient, and hence burdensome both in economic and practical terms for a manufacturer of the memory device.